Garber has spent his entire career in the sports industry, working in a variety of capacities in marketing, television and league administration. Before joining MLS, Garber was with the National Football League for 16 years.

Garber began his career in the sports business working for the National Wheelchair Athletic Association as the head of public relations before moving on to the public relations firm Ruder Finn and then Burson-Marsteller. While at Burson-Marsteller, he represented M&M Mars and met with the NFL about M&M Mars becoming a sponsor of the league. That meeting led to an offer from the NFL to be one of its first salespeople.[3]

Garber spent 16 years with the National Football League, finishing his tenure as the senior vice president/managing director of NFL International, where he oversaw all aspects of the NFL's business outside the United States, including the NFL Europe League. Garber began his career at NFL Properties in 1984 as a marketing manager and became the League's director of marketing in 1988. In 1992, he was appointed the NFL's senior vice president of business development and was responsible for a variety of television, special event and marketing activities.

Garber was appointed as the league's new commissioner on August 4, 1999[4] becoming Major League Soccer's second commissioner, succeeding Doug Logan. One of his first moves as commissioner was to bring the league more in line with the international standard, eliminating the shootout and letting the referee keep the time on the field.[5] Overtime and a fourth keeper sub were the only surviving non-standard rules, and both would go after the 2003 season.

Don Garber appears to be following a much longer-term growth strategy than all previous soccer league commissioners of the NASL and MLS have taken.[6] He has emphasized slow, steady growth of the league over many decades rather than attempting to force its way into the headlines (Beckham deal included) like the NASL did. Before Garber came into the Commissioner's office, the league had only one team in its own stadium, the Columbus Crew, whose Crew Stadium was built by Lamar Hunt in 1999. Due to this, most clubs were losing money. Garber met with league owners Philip Anschutz, Lamar Hunt and Robert Kraft around the turn of the millennium to decide what future actions should be taken to ensure the league's survival.[citation needed] Their decision was to build the sport following the model given by Lamar Hunt's Crew Stadium, and create Soccer United Marketing, an agency designed to manage rights to international soccer games and broadcasts in the U.S. The entire episode is characterized as critical to the league's survival. In 2003 another portion of the plan began to be implemented. This was the building of soccer-specific stadiums for all the league's teams. In 2003, the "cathedral of American Soccer", the Home Depot Center, was built to house the Los Angeles Galaxy, and both senior national teams. It was the second (behind Crew Stadium) of many soccer-specific stadiums in America, with four more built by the start of the 2007 MLS season. At the start of the 2015 MLS season, 15 of the league's 20 clubs play in soccer-specific stadiums or venues renovated with soccer in mind.

In order to address the complaints over the quality of the league's play, Garber and league owners embarked on a multi-pronged strategy. The first step taken was the creation of the MLS Reserve Division in 2005 that would give additional playing time to players not starting or playing much for the first team. Although the reserve division did not play in 2009 and 2010, it returned in a new format in 2011. In addition, MLS expanded its team rosters from 24 to 30. This would give the league's teams more flexibility and ability to compete over the season. Since 2013, MLS has focused on a partnership with the USL to help develop young players.[7]

Garber has estimated that 30 to 50 percent of the MLS’ fan base is Hispanic, and that he hopes the league will attract more Mexican players in the future. "We're trying to capture the heart and soul of the U.S. Hispanic, who is still very connected to home and has their favorite club in Mexico," he said. "We need to earn their trust and earn their respect."[8]

At the end of the 2006 MLS season, several more measures were introduced to improve the quality of play. The league mandated the creation of a youth development system, with U-14, U-15, U-16, U-18, U-20, and U-25 development squads [7]. Further, the league said that any player a team developed could be signed without giving them up to the MLS SuperDraft. Clubs can now sign an unlimited amount of Homegrown players.[9] Further increasing the incentives of MLS owners to invest in the mandatory teams is the increased portion of the transfer fees some of these players may bring, which will help a club's finances.

Another new competition initiative MLS undertook at the conclusion of the 2006 season was the creation of the Designated Player Rule, or "Beckham Rule". It is nicknamed after David Beckham as his signing with the Los Angeles Galaxy was the first use of the rule by a member club in January 2007. Garber has stated that fan research was one of the driving forces behind the decision to institute the Designated Player Rule. Garber and the league's owners also acknowledged that MLS needed a few more "marquee" players to boost interest and the long-term strength of the league in a quicker fashion.[10]

Commercially, Garber has also made huge strides over a long period of time. One of the most important of those commercial landmarks for the league was the first-ever TV rights deals that Major League Soccer agreed to with ABC/ESPN, Univision, Fox Soccer Channel, and HDNet. Between them the league took in approximately $20 million each year and was no longer responsible for producing the games. In 2015, MLS began a new eight-year media rights deal with ESPN, Fox and Univision, agreements that are priced five times higher than the average annual value of the league's previous media deals.[11] MLS also signed new international TV agreements in 2015, including deals with Sky Sports, Eurosport and Globosat.[12][13]

Furthering the league's financial well-being is the landmark decision to be the first professional sports league in North America to allow sponsor's names on the front of jerseys [8]. Real Salt Lake signed the first agreement with XanGo for an estimated $4–5 million over 4 years [9]. With a floor of $500,000 per year for a shirt sponsorship, of which $200,000 goes to the League as a flat fee, this is thought to be a way to increase owner's incentives to invest in their team(s). In addition, global brands such as Coca-Cola, Heineken, Audi and Johnson & Johnson signed league-wide sponsorships since the end of the 2014 season.[14][15]

Now, many teams generate multimillion-dollar sponsorships for their jersey-front sponsorships. Most jersey-front sponsorships generally run between $1–$4 million per year, although the Los Angeles Galaxy’s Herbalife agreement is reportedly more than $5 million per year.[16]

During Garber's tenure, ownership has been dramatically diversified. In 2001, there were just three investor-operators in the then 12-team league: Philip Anschutz's Anschutz Entertainment Group (AEG) controlled 6 teams, Lamar Hunt's Hunt Sports 3 teams, and Robert Kraft 1 team. The 2 league-operated teams, the Miami Fusion and the Tampa Bay Mutiny, were contracted after the 2001 season. When AEG sold its remaining interests in Houston Dynamo in 2015, the now 20-team MLS became for the first time a league without multiple-team operators.

Garber is married, has two adult children and lives in Montclair, New Jersey. He has received numerous industry honors,[29] and in 2011 was named by the Los Angeles Times as one of the top sports commissioners.[30]